1. Technical Field
The present invention relates to a fan motor with an improved airflow arrangement and an improved oil-proof and dust-proof structure.
2. Description of Related Art
A fan motor is a ventilating device that rotates a vane wheel attached to a rotary shaft, to thereby aspirate air from one side of the motor in the axial direction of the rotary shaft and discharge the air from the other side in the axial direction. The fan motor has a simple structure but provides a large airflow with a low static pressure, and is widely employed, for example, as a cooling fan and a ventilating fan for a personal computer.
An environment-resistant fan motor is normally incorporated with an outer-rotor type brushless motor. The outer rotor type brushless motor includes an armature having winding serving as an inner stator, and an excitation unit having a permanent magnet provided along the outer periphery of the stator, the excitation unit serving as an outer rotor. A vane wheel is fitted to the outer rotor. The vane wheel includes a plurality of vanes for generating an airflow inside a venturi casing.
In conventional environment-resistant brushless direct-current (BLDC) fan motors, the live part is covered with a resin member to protect the part where an electric current runs from moisture, oil, and dust.
The environment-resistant fan motors thus far developed include an axial flow fan in which a circuit board including coils of a core unit and electronic parts is molded with an epoxy resin that can be cured by an aromatic amine-based hardener, for example as disclosed in Japanese Unexamined Patent Application Publication No. 2006-246557.
The BLDC fan motor has a simple structure, and is hence often used in a severe environment where cutting oil and dust are floating in the air, such as a machinery assembly plant. In the case where the fan motor is turned off for a long period of time in the environment where cutting oil and dust are floating in the air, the floating oil and dust stick to the vanes and the hub unit of the fan motor.
When oil is deposited on the vane or the hub unit, the oil drips down along the sidewall of the hub unit, and intrudes into inside of the fan motor thus to firmly reside therein. In the case where the oil firmly resides inside the fan motor, the rotation of the rotor is disturbed, or the rotor may even be restrained and inhibited from rotating, when the fan motor is activated again.